1. Field of the Invention
The present invention relates to high temperature lamp apparatus with high efficiency that produces a beam of polarized light using a lamp bulb containing a fill under pressure that is energized with externally placed electrodes for vaporizing the gas. More particularly, the present invention relates to high power, high temperature electrodeless lamp in which light energy is polarized with a low temperature reflecting polarizer material and an insulator is positioned in between the vaporized gas and polarizing film material to prevent heat damage to the film.
2. Description of the Related Art
High power lamps are used for illumination applications beyond typical incandescent and fluorescent lamps. One type of lamp known as a high intensity discharge (HID) lamp consists of a glass envelope which contains electrodes and a fill which vaporizes and becomes a gas when the lamp is operated.
Recently, a patent issued for a high power lamp that utilizes a lamp fill containing sulfur or selenium or compounds of these substances. U.S. Pat. No. 5,404,076, issued to Dolan, et al., and entitled "Lamp Including Sulfur" discloses an electrodeless lamp utilizing an excited fill. The Dolan, et al., U.S. Pat. No. 5,404,076 is incorporated herein by reference.
Projecting systems are used to display images on large surfaces, such as movie or television screens and computer displays. For example, in a front projection system, an image beam is projected from an image source onto the front side of a reflection-type angle transforming screen, which then reflects the light toward a viewer positioned in front of the screen. In a rear projection system, the image beam is projected onto the rear side of a transmission-type angle transforming screen and transmitted toward a viewer located in front of the screen.
In prior co-pending U.S. patent application Ser. No. 08/581,108, entitled "Projecting Images," to Knox, filed Dec. 29, 1995, there is disclosed a method of displaying an optical image by projecting the image along an optical path and at an optical device interposed across the optical path, at one time reflecting the image from the optical device and at a different time permitting the image to pass through the optical device to be displayed. U.S. patent application Ser. No. 08/581,108, filed Dec. 29, 1995, is incorporated herein by reference. A projection system for such a display is disclosed in U.S. application Ser. No. 08/730,818, entitled "Image Projection System Engine Assembly," to Knox, filed Oct. 17, 1996, which is hereby incorporated by reference.
The image source for a projection system employs a light that must be of high intensity and preferably very efficient. Such a light is disclosed in U.S. patent application Ser. No. 08/747,190, entitled "High Efficiency Lamp Apparatus for Producing a Beam of Polarized Light," to Knox, et al., filed Nov. 12, 1995, which is hereby incorporated by reference. If an optical image is to be displayed by projection, it sometimes passes through an optical device interposed across the optical path. In the projection system of prior co-pending application Ser. No. 08/581,108, filed Dec. 29, 1995, one or more optical devices reflect the image at one time from the optical device and at a different time permit the image to pass through the optical device to be displayed. There will be a decrease in light intensity once the optical image strikes the optical device interposed across the optical path. Therefore, in projection systems where an optical device is interposed across the optical path there is a need for a projection engine with a high intensity light of improved efficiency.
One type of linear reflecting polarizer that is discussed in the above-referenced copending application is a reflecting polarizing film material is "DBEF" film material that can be obtained from Minnesota Mining & Manufacturing Company. DBEF (double brightness enhancement film) material is useful as an optical device for projecting video systems because it reflects substantially all light that does not pass through it. For example, it transmits substantially all light waves polarized to ninety degrees (i.e., "vertically" polarized light) and reflects substantially all light waves polarized to zero degrees (i.e., "horizontally" polarized light).
One of the problems of using a high intensity lamps (e.g., Dolan U.S. Pat. No. 5,404,076) with film type polarizers (e.g., 3M DBEF) is that of heat damage. Such lamps can generate heat of thousands of degrees (e.g., 3000.degree. F.) while the reflecting polarizer film material can have a low temperature operating range of below 80.degree. C. or as is typical for plastic (acrylics).